Remarkable story in this NPR podcast (ignore the stupid Batman title) with fascinating insight on how echolocation developed and the plasticity of the human brain. To summarize, neuroscientists found that Daniel Kish, who is blind, not only was able to train himself to echolocate with clicking sounds, but also was using the otherwise unused vision centers of his brain to do so.

More details: "When he heard the sounds of click echoes, [his] calcarine cortex – a part of the brain that normally deals with vision – lit up ... When they heard the sounds of echoes reflecting from moving targets, they showed activity in areas that deal with movement. Neither of the two sighted volunteers reacted in the same way – to them, the recordings were just noises ... The calcarine cortex seemed to be specifically tuned to echoes, as opposed to other noises. It became far more active when Kish and Bushway heard the sounds of soft echoes than when they heard echo-less recordings, even though the auditory cortex reacted similarly to both sets of sounds. This suggests that both men have diverted a part of their brain, which would normally deal with sights, to handling the sound of echoes."http://blogs.discovermagazine.com/notrocketscience/2011/05/25/the-brain-on-sonar-%E2%80%93-how-blind-people-find-their-way-around-with-echoes/